The present invention relates to an apparatus for continuous laser welding of adjacent longitudinally extending edges of generally tubular shaped members such as can bodies and the like which are moved relative to a laser welding device for welding the edges. More particularly, the invention relates to a mandrel for continuous laser welding of such members so that the potential damage to the members during welding is minimized while the quality and appearance of the weld are enhanced.
The applicability of laser welding for joining adjacent longitudinally extending edges of generally tubular shaped members is known. For example, in U.S. Pat. No. 4,152,573 to Saurin, et al., a method and apparatus for laser welding metal can bodies are disclosed. However, such an apparatus is not suitable for the type of continuous, high-speed operation necessary for production in most commercial applications. In particular, in Saurin, et al. the generally tubular shaped members are each fixedly clamped on both sides of the weld joint area by clamping bars of a vise or fixture. During welding the vise or fixture and the member clamped therein are advanced relative to a laser welding device to accomplish the welding. Thus, with such known apparatus an individual member to be welded must be first clamped, then welded, and thereafter unclamped from the vise or fixture before a second member can be processed. Such an apparatus is not suitable for commercial applications where continuous, high rates of production, such as 400-600 can bodies per minute, are necessary or desirable.
The Z-bar guide apparatus disclosed in applicant's aforementioned U.S. Pat. Nos. 4,272,004 and 4,354,090 make it possible to position and guide adjacent longitudinally extending edges of members so that the members may be continuously advanced and laser welded with a lap or butt joint. To accomplish this a means for advancing the members along the Z-bar and past the welding station must be provided. As indicated in the aforesaid patent and copending application, conventional chain type conveyors, drive rollers, reciprocating pistons or push rods or the like may be used to advance the members. Such an arrangement permits the continuous, high-speed laser welding of the adjacent longitudinally extending edges of the members. However, applicant has found that when laser welding such members, operator safety may be impaired and/or damage may occur to the members outside the weld area as a result of light from the laser beam which has passed through the weld joint, such as where the laser beam keyholes through the adjacent edges during welding. In the case of a metal tubular member being laser welded, light passing through the weld joint area can strike the opposite side of the tubular member and damage the member and/or a protective coating which has been applied thereto.
Another problem that may occur during the continuous laser welding of members with a Z-bar guide apparatus of the aforementioned type relates to the welding of the trailing ends of the members. That is, as the longitudinally extending edges of the members are advanced through the Z-bar and past the laser welding station and ultimately leave the Z-bar, they are no longer positioned and guided by the Z-bar and may become misaligned with respect to the Z-bar. If this occurs the trailing edges being welded may be moved or shifted so as to adversely affect the weld quality, particularly in the case where the trailing ends of the members leave the Z-bar before they are actually welded by the laser beam.
It has also been found that as a result of laser welding of adjacent longitudinally extending edges of the members, a slight weld upset may project outwardly from the surface of the members. Such a weld upset may be undesirable in the finished product from the standpoint of function and/or appearance.
An object of the present invention is to provide an apparatus for continuous laser welding adjacent longitudinally extending edges of generally tubular shaped members which minimizes or avoids the aforementioned problems which may occur in continuous, high-speed laser welding. More particularly, an object of the present invention is to provide an apparatus for continuous laser welding which enhances operator safety and prevents damage to the welded member outside the weld area by light and/or weld debris from the laser beam.
A further object of the present invention is to provide an apparatus for continuous laser welding adjacent longitudinally extending edges of generally tubular shaped members such as can bodies and the like, which supports and guides the members as they leave the Z-bar so that they do not become misaligned with respect to the Z-bar and adversely effect the weld at the trailing ends of the members.
An additional object of the invention is to provide an apparatus for continuous laser welding adjacent longitudinally extending edges of generally tubular shaped members which enables the weld upset on the members to be smoothed in a continuous manner following the laser welding operation.
These and other objects of the invention are attained by providing an apparatus for continuous laser welding adjacent longitudinally extending edges of generally tubular shaped members comprising Z-bar guide means for positioning and guiding the edges as the members are moved toward a welding area with a laser welding means for welding the edges, and a mandrel connected to the Z-bar guide means and extending internally and in the direction of movement of the members, the mandrel including laser beam dump means positioned adjacent the welding area for absorbing light from a laser beam produced by the laser welding means. With such an arrangement the light from the laser beam which passes through the weld joint area is absorbed for operator safety from reflected light and so that damage to the tubular shaped members and any coatings thereon is avoided.
According to a disclosed, preferred embodiment of the invention the laser beam dump means includes receptacle means for receiving light from the laser beam. The receptacle means is provided with an opening through which the light can enter and the inside of the receptacle means is a dark color for absorbing the light. In particular, the receptacle means in this disclosed embodiment is in the form of a cup which is made of an aluminum alloy. The inside of the cup is anodized black to absorb the light.
As another feature of the invention the receptacle means includes gas inlet means for receiving a gas so that the gas can pass through the receptacle means and out the opening therein to provide a gas, such as an inert shielding gas, in the welding area adjacent the edges being welded. In the disclosed embodiment the receptacle means is removably positioned within a cooling jacket for cooling the receptacle.
The mandrel of the invention further includes roller means for internally supporting and guiding the generally tubular shaped members as they leave the Z-bar. The roller means is located in the mandrel downstream of the laser dump means in the direction of movement of the members and includes a first roller which preferably contacts the members in the area of the weld. Such an arrangement prevents the tubular members from becoming misaligned as they leave the Z-bar to ensure that the trailing ends of the members are properly aligned during welding.
The first roller of the roller means in the mandrel includes support shaft portions extending from opposite sides of the first roller. These support shaft portions are supported on respective pairs of rollers provided on the mandrel. In the disclosed embodiment the respective pairs of rollers are bearings and the support shaft portions of the first roller are supported on the outer races of the bearings. Means are provided for removably mounting the plurality of rollers on the mandrel so that they may be readily repaired or replaced when necessary. According to one form of the invention the means for removably mounting the plurality of rollers includes slots formed in the mandrel which receive shafts upon which the plurality of rollers are mounted. According to another form of the invention the means for removably mounting includes holes extending through the mandrel for receiving shafts upon which the plurality of rollers are mounted.
An additional feature of the invention involves the provision of a second roller in a position for engaging the members in the area of the welded edges on a side of the members opposite the first roller of the roller means. According to one form of the invention means are provided for yieldably biasing the second roller in the direction of the members and the first roller to subject the members to a predetermined force. This arrangement permits the weld upset to be reduced and smoothed.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, one preferred embodiment in accordance with the invention.